Malaysian Prime Minister Najib Razak said on Friday the central bank governor has asked the police to investigate the Wall Street Journal for leaking a confidential document related to an inquiry into scandal-hit government fund.

"They (police) will have to investigate. Publishing confidential documents under OSA (Official Secrets Act) is a very serious action on (their) part. And they must be able to provide us with the answers," Najib told reporters at a news conference.

Earlier on Friday, the Wall Street Journal published a copy of a letter said to be from Malaysia's central bank and addressed to Hasan Arifin, the chairman of a parliamentary committee investigating the state investment fund, 1Malaysia Development Bhd.

When asked if the letter was authentic, Najib said: "I don't know. Let the police investigate...we need to find out first."

A spokeswoman for Dow Jones, which publishes the Wall Street Journal, said: "We stand behind our fair and accurate reporting of this evolving story and remain committed to providing robust coverage of events in Malaysia."